POLICE closed the A611 Annesley bypass overnight on Saturday due to a birthday party taking place on private land near the bypass - and the A611 finally re-opened late on Sunday afternoon.
The road was closed due to a large number of cars being parked on it, making it dangerous for motorists, according to police.
A Nottinghamshire Police spokesman said it was re-opened onceit was safe to do so.
He added: “We are launching an investigation into the legitimacy of the gathering and hopefully this will not happen again.”
It has been reported that around 200 people from all over the country had been dancing at the all-night party in the woodland with the consent of the landowner.
Revellers still at the site on Sunday afternoon could be seen clearing up the area.